The present invention relates to a device for continuously producing a tubular structure comprising a spiral winding made of at least one shaped wire of large cross section, particularly, although not exclusively, a noninterlocking wire delivered from a reel of wire and, as appropriate (that is to say when a noninterlocking wire is being used) at least one locking wire delivered from a reel of locking wire, which device will hereafter be known as a wire-spiralling machine.
The applicant company has developed and marketed for various applications, and particularly for offshore oil production, flexible tubular pipes which have high mechanical properties, particularly as regards the tensile strength and the ability to withstand the pressures exerted both from the outside of the pipe and from the inside, by the transported products particularly hydrocarbons.
Reference may, for example, be made to the patents EP-A-0,148,061 and EP-A-0,494,299, which disclose an example of a general structure for flexible tubular pipes, and a device for producing such a structure. In these two documents, the question is one of producing a tubular structure consisting of a spiral winding (generally the carcass of a flexible pipe) from an interlocking strip. The strip has a cross section, generally likenable to an S or a Z, which allows each laid turn to catch on to the previous turn by virtue of their complimenting profiles. In the former of these documents, a spiralling machine that is suitable for these relatively flexible strips is described. The machine comprises a circular plate rotating about a horizontal axis that coincides with the longitudinal axis of the tubular structure that is to be formed and which, on one same face where the laying of the spiral winding takes place, supports a strip-feed reel, guide rolls, a collection of shaping wheels and press rolls cooperating with a lay mandrel to form the turns of the winding. The same spiralling machine is discussed again in the second document, it being specified that it is possible simultaneously to use two reels paying out either two interlocking wires or one noninterlocking wire and an additional wire which produces the locking through combination with the first wire. A first alternative form of the device, inspired by document U.S. Pat. No. 4,783,980 is described, together with a second alternative form, inspired by document U.S. Pat. No. 4,895,011. In the latter alternative form, profiled strips are unwound from stationary supply reels and are wound externally into turns around the rotating plate, the innermost turn of this winding being taken over a turn roll to despatch the strips to the lay point.
There are also known flexible tubular pipes which comprise a metal reinforcing layer, such as an internal carcass or a layer which provides resistance to the internal or external pressure, known as the pressure-armour layer. The reinforcing layer consists of the spiral winding of an interlocking wire of the shaped wire type which has a solid cross section in the shape of a Z, such as the wires known by the name of "zeta". Documents FR-A-2,052,057 and FR-A-2,182,372 describe such windings, respectively of relatively thick wire wound at a short pitch and of wire of a flattened cross section wound at a large pitch, and the means for manufacturing then. These documents in particular comprise means for giving the wire a permanent sword-blade deformation prior to winding. The shaped wires involved in the techniques described in these two patents and in the current state of the art of wire spiralling have a thickness which at its maximum, is 10 mm or, exceptionally, is 12 mm.
Although the interlocking wires that consist of a strip of typically S- or Z-shaped cross section may prove satisfactory up to a certain level of forces or stresses involved, it has become apparent that in order to produce the carcasses or pressure-armour layers of flexible pipes, particularly of those intended for a more arduous environment (for example very high internal pressure, very deep water, very large diameter of flexible tube, high dynamic stressing), it was necessary to develop tubular structures produced by co-winding a noninterlocking wire with an additional element whose task was to catch the adjacent turns of noninterlocking wire together. The noninterlocking wire is advantageously a wire of the shaped wire kind, relatively thick, preferably of solid cross section comprising parts in relief. The cross section of the wire advantageously is in the shape of a T or a U rather than simply having a shaped strip in the case of a carcass or an S- or Z-shaped interlocking wire, in the case of a pressure-armour layer. The additional element, which hereafter will simply be called a locking wire, is for example U-shaped, or may even consist of a second wire of identical shape to the first, but arranged the opposite way round and wound around the first wire (straddling two adjacent turns of the first wire), if the catching reliefs of the shaped wire are designed for this. On this subject, reference will be made to EP-A-0,431,142 and WO-A-96/18060, the teachings of which are incorporated by reference. In the latter document, the manufacture of the spiral structure is merely touched upon: it is simply stated that the T-shaped wire can be spiralled in the same way as a noninterlocked wire of an additional pressure-armour layer or binding (that is to say one which generally consists of a flat. This is certainly possible in the case of T-shaped wires of relatively small cross section, the relatively low stiffness of which allows the wire to be routed and wound without particular problems of guidance, bending, unbending, etc. This becomes no longer true when the cross sections of the shaped wires are considerable and make the rigidity of the wire itself considerable-. By way of indication, the cross-sectional thickness of the Z-shaped interlocking steel wires used ranges from 4.8 mm to 10 mm, or even exceptionally 12 mm. The noninterlocking T-shaped wires specifically targeted by the invention are themselves 12 mm, 14 mm, 16 mm thick, or even thicker.
As far as the applicant company is aware, there does not yet exist any machine capable of correctly and automatically winding such wires, and this is therefore the subject of the present invention.